CHEMOSPHERE
·
2018
·
IF 4.427
Yiqun Gan,Shengcun Ma,Xiaoqi Guo,Baiyang Chen,David Jassby
Chloral hydrate (CH) is a common disinfection by-product found in treated water, and its effective control is important to human health. This study evaluated the effects of some environmental factors (e.g., pH, CH dosage, typical ions) and operational variables (e.g., lamp power, irradiation time) on CH photolysis efficiency via low-pressure mercury lamp–induced ultraviolet (LPUV) at 254 nm. The results demonstrated that the photolysis rate increased significantly with increasing pH from 7.0 to 10.5 and lamp power from 6 to 12 W. Meanwhile, the presence of nitrate, iodide, or free chlorine facilitated CH photolysis, whereas the existence of natural organic matter hindered the process. Together, these factors may help explain varying CH photolysis in different types of waters: seawater > ultrapure water > tap water > lake water. In addition, the initial CH dosage also played an important role, with higher CH being degraded more slowly. Mechanistically, although no catalyst or oxidant was added, CH photolysis was to some extent inhibited by a hydroxyl radical quencher, tert -butyl alcohol, suggesting that indirect photolysis was also responsible for CH loss. In terms of reaction products, the CH photolysis yielded primarily chloride ions and carbon dioxide, thus supporting mineralization as the key pathway. The results may help better understand the control of CH in water using UV.
研究领域:
环境科学
·
水处理工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
CHEMOSPHERE
·
2016
·
IF 3.698
Shengcun Ma,Xiaoqi Guo,Baiyang Chen
Chloral hydrate (CH) is a disinfection byproduct commonly found in disinfected water, and once formed, CH may undergo several transformation processes in water distribution system . In order to understand its fate and occurrence in water, this study examined several factors that may affect the stability of CH in water, including pH, temperature, initial CH concentration, typical anions, and the presence of free chlorine and monochloramine. The results indicated that CH was a relatively stable compound (half-life ∼7 d for 20 μg/L) in ambient pH (7) and temperature (20 °C) conditions. However, the hydrolysis rate can be greatly facilitated by increasing pH (from 7 to 12) and temperature (from 20 to 60 °C) or decreasing initial CH concentration (from 10 mg/L to 20 μg/L). To quantify the influences of these factors on the CH hydrolysis rate constant (k, 1/h), which spans five orders of magnitude, this study developed a multivariate model that predicts literature and this study’s data well (R 2 = 0.90). In contrast, the presence of chloride, nitrate, monochloramine, and free chlorine exhibited no significant impacts on the degradation of CH, while the CH loss in non-buffered waters spiked with sodium hypochlorite was driven by alkaline hydrolysis. In terms of reaction products, CH hydrolysis yielded mostly chloroform and formic acid and a few chloride, which confirmed decarburization as a dominant pathway and dehalogenation as a noticeable coexisting reaction.
研究领域:
环境科学
·
化学工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
JOURNAL OF HAZARDOUS MATERIALS
·
2020
·
IF 9.038
Xiaoxiao Zhang,Zhonglin Chen,Jing Kang,Shengxin Zhao,Binyuan Wang,Pengwei Yan,Fengxia Deng,Jimin Shen,Wei Chu
In this study, kinetics, influencing factors and potential mechanisms involved in the degradation of chloral hydrate (CH) by UV/peroxymonosulfate (PMS) process were demonstrated. The degradation rate of CH could reach 89.6% by UV 254 /PMS process, significantly exceeding UV 300 /PMS (0.7%), UV 350 /PMS (6.3%), UV 254 direct photolysis (9.0%) and PMS alone (0.0%) processes. CH degradation in UV 254 /PMS system followed pseudo first-order degradation kinetics with an apparent rate constant of 0.186 min −1 , which was suppressed by Cl − and HCO 3 − . The optimal pH for CH degradation was around 5.0. Direct mineralization accounted for the CH degradation in UV/PMS system. Interestingly, the addition of PMS at the neutral condition before UV irradiation transferred CH into trichloroacetic acid (TCAA). The transformation efficiency of CH into TCAA at 10 min was enhanced from 2.17%–40.38% with the elevation of initial pH from 7.0–8.0. The subsequent exposure of UV lamps ceased the transformation of CH into TCAA and facilitated the direct mineralization of CH, but it did not work in the refractory TCAA degradation. Finally, it was revealed that HO predominantly participated CH degradation in UV/PMS process, while O 2 − was responsible for the transformation of CH into TCAA by addition of PMS before UV irradiation.
研究领域:
环境科学
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化学工程
✓ 已验证
产品关联
DOI
PubMed
高影响因子
Nature Communications
·
2024
·Vol. 15
·期 1
·1-10
·
IF 14.7
Zhang Xun,Feng Ximin,Guo Wenqi,Zhang Chengjian,Zhang Xinghong
Polyvinyl chloride (PVC) is the world’s third-most widely manufactured thermoplastic, but has the lowest recycling rate. The development of PVC-like plastics that can be depolymerized back to monomer contributes to a circular plastic economy, but has not been accessed. Here, we develop a series of chemically recyclable plastics from the reversible copolymerization of cyclic anhydride with chloral. The copolymerization is highly efficient through the anionic or cationic mechanism under mild conditions, yielding polyesters with tunable structure and properties from multiple commercial monomers. Notably, these polyesters manifest mechanical properties comparable to PVC and polystyrene. Meanwhile, such polyesters are flame-retardant like PVC due to high chloride content. Of significance, these polyesters can be depolymerized back to starting monomers at high temperatures owing to the reversibility of the copolymerization, leading to a circular economy. Overall, the readily available monomers, simple synthesis, advantageous performance, and practical recyclability make the polymers promising for applications.
研究领域:
材料科学
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化学工程
·
环境科学
✓ 已验证
DOI
PubMed
高影响因子
危险品化学品经营许可证（带存储）